An important advantage of the drive technology is high storage capacity at relatively lower cost compared to flash memory. In addition to areal density, increases in linear density for a given rpm and form factor of drive increase the maximum data rate. Server applications where access to large amounts of mission critical data is essential also requires high data rates. High data rates can be important for both conventional and electrically assisted magnetic recording (EAMR) recording technology. Innovations in head design, coil design and magnetic materials are necessary to achieve high data rates.
To achieve high data rates, coil designs can be important. Coil designs for writers can be used in both conventional perpendicular and EAMR heads. EAMR heads generally require a large write gap (e.g., about 1.5 um) as optics needs to be sandwiched between the main pole (P1) and the return pole (P2) compared to conventional perpendicular writers where write field gradient requires a small gap (e.g., about 30 nm) between the main pole and the return pole. Write gap length in the conventional perpendicular design needs to be matched to the distance between head to the soft under layer (SUL) in the media, which is typically about 30 to 40 nm from the air bearing surface (ABS). For EAMR designs, either the SUL generally needs to be completely removed or SUL generally needs to be deposited below the heat sink layer, thereby increasing distance between the head and the SUL. Because of the large write gap and larger distance between the head and the SUL layer, the EAMR design generally requires more coil turns to achieve head saturation for pre-amp current below approximately 50 mA. As a larger number of coil turns are often required, low inductance is needed to achieve high data rates. Therefore, a short yoke length and a helical coil are preferred over pancake coils typical of EAMR head designs. However, because of the short yoke and small coil pitch, the resistance of the helical coils can be large. The large coil resistance provides large write pole tip protrusion due to the close proximity of the coils to the return pole or P2. Therefore, an improved coil design can require reducing the coil resistance. As such, a coil design is needed that minimizes inductance and resistance while maintaining short yoke length.